Prerequisite Tree¶
Definition¶
The Prerequisite Tree (PRT) uses necessary-condition thinking to turn a distant or seemingly impossible objective into an ordered set of intermediate objectives, each one existing specifically to overcome a named obstacle. Unlike a Transition Tree — used when you already know roughly what actions to take — the PRT is for the situation where "all you are faced with are the reasons that your objective will be difficult to accomplish": you list the obstacles, invent an intermediate objective that neutralizes each obstacle, and then sequence those intermediate objectives by their own necessary-condition dependencies.
In the Book¶
Chapter 10 opens with the Apollo moon landing as its framing case: Kennedy's 1961 commitment to land a man on the moon "before this decade is out" gave NASA engineers a goal reachable only by breaking the gap between "orbiting the earth" and "landing on the moon and returning safely" into an obstacle-by-obstacle path — accomplished, ultimately, on July 20, 1969. Scheinkopf contrasts this with the three typical responses to a goal that feels too hard: quietly lowering it, shelving it as a "someday" dream, or waiting passively for it to happen. The PRT's process — define the tree's purpose and objective, list obstacles and the intermediate objective that overcomes each, map the implementation order of those intermediate objectives, then implement — is illustrated with objectives like "on-time shipping performance is consistently 99-100%" or "my book is published," each stated in present tense to keep the plan grounded in what must actually exist, not what might exist. In the Full Analysis (Chapter 11), the PRT's objectives are literally the injections carried over from a Future Reality Tree, and its output — the sequenced intermediate objectives — becomes the first half of the answer to "how to cause the change."
Why It Matters¶
"That's impossible" is usually a claim about obstacles you haven't yet named, not a claim about physics — and naming each obstacle explicitly, then inventing the specific milestone that neutralizes it, converts an overwhelming goal into a sequence of locally achievable steps without lowering the goal itself. This is the general antidote to goal paralysis in any domain: replace "how do I get all the way there" with "what specifically is in my way right now, and what would remove it."